Apparatus for tuning klystron cavities



March 29, 1960 J. v. LEBACQZ 2,930,923

APPARATUS FOR TUNING KLYSTBON CAVITIES Filed June 28, 1957 W 2W //y INVENTOR. JEAN M LEBACOZ A T TORNE V United States Patent O APPARATUS FOR TUNING KLYSTRON CAVITIES Jean V. Lebacqz, Menlo Park, Calif., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application June 28, 1957, Serial No. 668,828

2 Claims. (Cl. BIS-5.43)

This invention relates to klystrons and more particularly to an apparatus for tuning klystron cavities.

In prior art tuning schemes such as represented by US. Patents Nos. 2,490,030, 2,515,280 and 2,400,743, the cavities of the klystrons are tuned by varying the gap spacing. However, the prior art structures suffer from the deficiencies of requiring a rather complicated external tuning mechanism, causing an increase in the over-all drift length concomitant with the tuning. and posing the rather difficult problem of maintaining sufficiently accurate over-all alignment of the various sections of the drift tube, especially in cases of multi-cavity klystrons with long drift tubes.

An object of the present invention, therefore, is to provide a tuning apparatus for klystron cavities which will accomplish the gap tuning without an accompanying change in the over-all drift length of the klystron tube and which will be simple in construction and easy to operate without problems of alignment.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 represents a fragmentary cross-sectional view of a klystron showing a preferred embodiment of the tuning mechanism of this invention; and

Fig. 2 is a cross-sectional view taken along the line 22 in Fig. 1.

Reference is now made. to the drawing. The numeral 2 represents a main, gap-tuned cavity of more or less conventional design aligned with a second main, gaptuned cavity 4 and maintained in rigid relation thereto by any convenient structure such as the stiffening strut 6. Interposed between the two main cavities is an auxiliary cavity 8 provided with amode shifter ordetuning ring 10. To vary the spacing of the gap in main cavity 2, the drift tube section 12 is arranged to be displaced by means of tuning screws 14 (shown as 3 in number by way of example) acting on a spider 16 firmly attached to the drift tube section 12. The drift tube section 12 is sealed in conventional fashion. to the flexible diaphragm 18 forming one end wall of the cavity 2. The tuning screws 14 bear inbushings 20 in a fixed plate 22, only a fragment of which is shown.

The detuning ring 10 is empirically designed to keep all resonances of the auxiliary cavity 8, which can be called the untuned cavity, outside of the tuning range of the main cavities' In tuningthe main cavity 2 the screws 14 are rotated to change the gap spacing involving a movement of only section 12 of the drift tube. This axial movement of section 12 is accomplished without any corresponding movement of the drift tube section 24 or the drift tube section 26. During the process of tuning the main cavity the so-called untuned cavity 8 is, of course, actually being tuned, but it is and remains untuned in the sense that its resonant frequency curve never crosses the resonant frequency curve of the main cavity. In tuning the main cavity 4 the drift tube section 28 is moved axially relative to tube section 26 by any convenient means, the movement being facilitated by aflexible diaphragm or the like (not shown) to which tube section 28 is connected. With this construction there is no change in over-all drift length during the tuning process. Also, the problem of keeping the various drift tube sections in over-all. axial alignment is greatly simplified.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is: v

1. An electron'discharge device comprising a first main cavity resonator and a second main cavityresonator, said resonators having alignedopenings in their adjacent walls through whicha stream of electrons can pass from one to the other resonator; an auxiliary cavity resonator interposed between said first two resonators, said auxiliary cavity resonator having its resonant frequencies completely outside the tuning range of said main cavities; means rigidly and permanently retaining in fixed,

immovable relation to onev another'the side walls, extending axially in the direction of the electronstream,

of all three said resonators; said first main cavity resonator and said auxiliary cavity resonator having adjacent flexible end walls connected by a drift passage tube; and means for displacing said drift passage tube with respect to said resonators to tune said first main resonator.

2. The device of claim 1 wherein said last named means includes a spider fixed rigidly to said drift passage tube and a plurality of screws fixed against axial movement and threaded into said spider whereby rotation of said screws in either direction produces concomitant axial motion in respective opposite directions I of said spider, and hence said drift passage tube, to tune ,said first main resonator.

References Cited in the file of thispatent I Veronda June 1, 1954 Patented Mar. 29, 1960v 

